The invention relates to an apparatus for accommodating and making electrical contact with a luminous means in a spotlight.
DE 198 16 364 C2 has disclosed a spotlight for film, studio and stage lighting and further application areas which has a spotlight housing, which is used for accommodating a luminous element, a transparent cover disk in the form of a protective disk or a lens disk and a reflector. Lights or lamps, preferably discharge lamps with a base at one end, in a vertical or horizontal installed position, i.e. in each case perpendicular to the optical axis, or in an axial installed position, i.e. in the optical axis, are used as luminous means or luminous elements.
The lamps have a gas-filled glass body with electrodes arranged therein, a lamp base, through which the feed lines are guided to the electrodes, and two or more contact pins, which are arranged at that end of the lamp base which is opposite the glass body. The contact pins are inserted into the plug-in sockets of a lampholder, which is connected to the lamp housing, so as to be connected to a voltage source, it being necessary for there to be a tight fit between the plug-type sockets and the contact pins for the high levels of lamp current which need to be transmitted.
At the same time, the contact pins for example of discharge lamps with a base at one end act as fixing means for the discharge lamp. Since with increasing lamp powers the physical size of the discharge lamps and in particular the physical length of the glass body and the lamp base also increase, the lamps with relatively high lamp powers have such a physical size that, in particular in a horizontal installed position of the discharge lamps, considerable forces are exerted on the contact pins, which, in addition to the supply of power, also act as fixing contacts.
These forces result in the contact between the contact pins and the plug-type sockets of the lampholder being impaired, which is associated with increased transfer resistance in the transmission of the lamp current, a displacement of the lamp out of the focal point of the reflector and, as a result of this, reduced luminous efficiency and with the forces being transmitted into the lamp interior, which can result in impermissible voltages and ultimately in failure of the lamp.
The disadvantages associated with the lamp being mounted exclusively via the contact pins do not only take effect in the steady-state range in terms of the physical size of the lamp, however, but in particular also in the dynamic range in the case of transport of a spotlight or its operation with jerky pivoting movements, impacts on the lamp housing and the like.
In order to be able to use a lamp housing for lamps with different lamp base diameters without replacing an accommodating device and to use the contact pins of the lamps exclusively for transmitting the lamp current, in the case of the lamp housing known from DE 198 16 364 C2 the accommodating device comprises clamping jaws, which engage around the lamp base and can be adjusted by means of the adjusting device into an opening position, in which the lamp base is released, and into a locking position, in which the lamp base is fixed. The adjusting device comprises a latch with two sloping faces, which have an identical geometric design and bear against the upper and lower clamping jaws in such a way that, when the latch is adjusted, the clamping jaws are spread radially apart.
During actuation of the adjusting device for the purpose of opening and closing the clamping jaws, at the same time opening and closing of the plug-type sockets which accommodate the contact pins of the luminous means also takes place, with the result that by simultaneously releasing the contact pins in the case of an actuation of the adjusting device for the purpose of opening and closing the clamping jaws the luminous means can be removed easily by the luminous means base being released or a luminous means can be inserted in the opening position of the lamp holding device.
In the case of spotlights with luminous means with a base at one end, the luminous means are plugged through the reflector with the front-side cover of the front side of the spotlight open and are fixedly clamped in the luminous means holder positioned behind said reflector. Only when the luminous means bears centrally and straight against the end stop of the luminous means holder can the clamping apparatus be actuated since otherwise the luminous means holder, the plug-type sockets or the luminous means base and the contact pins would be damaged by breakage, flashovers or corrosion.
With increasing power and therefore increasing physical size of the luminous means, however, there are problems associated with the correct insertion of the luminous means into the luminous means holder of the spotlight. On the one hand, the luminous means needs to be observed from the front when it is inserted into the luminous means holder in order to be able to insert the luminous means straight, i.e. with mutually aligned contact pins of the luminous means and the plug-type sockets of the luminous means holder, while on the other hand the operator needs to firmly hold and center the luminous means with one hand and operate the clamping apparatus with the other hand, and the operating elements of said clamping apparatus are usually found on the side of the spotlight housing. In this case, however, in the case of relatively high spotlight powers with correspondingly large spotlight housings the operator can no longer stand sufficiently far in front of the spotlight in order to be able to at the same time observe the straight insertion of the luminous means and operate the clamping apparatus.
A further problem consists in the fact that, on the one hand, a reflector opening is desired which is relatively favorable in optical terms for the reflection of the light emitted by the luminous means and is therefore as small as possible, but which, on the other hand, makes the visual control when inserting the luminous means into the luminous means holder more difficult since the view of the luminous means holder is impeded, in particular if the luminous means has already been partially inserted into the luminous means holder, with the result that the operator can no longer identify whether the luminous means has been inserted correctly or is skew and consequently the contact pins of the luminous means make contact with the plug-type sockets of the luminous means holder only to an insufficient extent.
A displacement of the clamping apparatus for force-fitting and/or form-fitting clamping-in of the luminous means base toward the front side of the spotlight housing would not result in any substantial improvement of the visual control during the insertion of the luminous means into the luminous means holder since the visual control would in any case be impaired by a narrow reflector opening, with the result that improved visual control would only be possible with an enlarged reflector opening, with the downside of impaired beam reflection and poorer optical properties of the spotlight.
In order to detect a correct fit of a lamp base in a lampholder, it is known from JP 09-185978 A to provide a recess in the lamp base, with a torsion spring arranged on the bottom of said recess, the ends of said torsion spring being bent upward and having engagement projections, which engage in corresponding engagement recesses in the inner wall of the lampholder. If the lamp base is inserted into the lampholder, this results in rotation of the torsion spring and, when the engagement projections engage in the engagement recesses, an acoustic signal is produced.
JP 2000-340316 A has disclosed a device for detecting an insufficient connection between a lamp base of a discharge lamp and a lamp holding device, which connection comprises a connecting cable and a fixing clamp, which can only be connected to the lampholder when the lamp base is completely connected to the lampholder.
DE 296 23 442 U1 has disclosed a lighting device with a radiator which has a base at one end, in which lighting device a connection of the radiator to a holder is ruled out if the radiator is unsuitable. For this purpose, the holder for accommodating the radiator is connected to a sensor element, which receives magnetic or optical pulses, while that part of the base which faces the holder is provided with a marking element, which emits magnetic or optical pulses, which are received by the sensor element once the marking means has been excited by excitation means such that it emits the pulses.
GB 2072958 A has disclosed a discharge lamp whose base is connected to a holder, which contains a device for producing a high voltage from an AC voltage. The holder has a recess at whose end a high-voltage contact is arranged, which is connected to a pin protruding from the base of the discharge lamp. Furthermore, contacts for preheating the cathode and contacts corresponding to a peripheral conductive collar of the lamp base are provided in the recess of the holder, with which contacts a signal applied to the contacts of the holder is short-circuited. The short-circuiting of the contacts signals the correct fit of the lamp base in the holder emitting the high voltage.
These known apparatuses for detecting the correct fit of a lamp base in a lampholder or for preventing the insertion of an unsuitable luminous means into a lampholder have a very complex configuration and require corresponding devices both on the lamp base and on the lampholder, with the result that they are only capable of functioning when the lamp base of the luminous means is provided with the corresponding detection means. The complex configuration of the detection devices also results in increased sensitivity to interference, which results in faulty detections, in particular taking into consideration the high temperatures in the region of the lamp base and the lampholder.